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  <script>
    // 利用递归函数求 1~n 的阶乘 1 * 2 * 3 * 4 * ...n

    let result = 1;
    function fn(n) {
      if (n == 1) {
        return 1;
      }
      return n * fn(n - 1);
    }

    console.log(fn(5));
  </script>
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